1. Field of the Invention
A fluid extraction device to remove fluid contaminants from the vadose zone of unsaturated subsurface area by selectively evacuating liquid and gas therefrom.
2. Description of the Prior Art
Numerous devices and methods have been developed to remove volatile contaminants from the vadose zone; that is the area between the earth's surface and the underground water table.
Contamination of the subsurface ground results from spills, leakage from storage facilities or surface discharges. These contaminants eventually percolate into the groundwater to create a health hazard.
Circulation systems for leaching the contaminants from contaminated media above the water table have been developed such as shown in U.S. Pat. No. 4,167,973. Contaminant vapors may be extracted from contaminated underground areas by means of a plurality of elongated perforated collection elements as taught in U.S. Pat. No. 4,183,407. However, such a system is limited to removal of contaminants from relatively shallow.
U.S. Pat. No. 4,369,839 shows a casing vacuum system which applies a controlled vacuum to the space within the casing of an oil well in order to maintain the gas pressure in the well within a certain range to improve the recovery of petroleum from the well. A water accumulator protects the vacuum pump from water damage. A condensate accumulator collects the gas drawn from the well and condenses a portion into liquid hydrocarbons. A mercury vacuum switch maintains the gas pressure in the well within the optimum range for recovery of petroleum.
U.S. Pat. No. 4,544,037 discloses the production of methane from an underground wet coal seam initiated by drilling a well from the surface of the earth through the seam. High pressure gas is injected into the seam to drive water away from the wellbore. Initial gas production is followed by a mixture of return injected gas and methane, free methane from the fracture system of the coal and finally methane from the coal.
U.S. Pat. No. 2,910,002 relates to a dual-zone pumping apparatus of the sucker rod type for simultaneously producing oil and gas from two formations or zones within a single well bore without commingling the oil and gas from either formation.
U.S. Pat. No. 4,823,880 teaches a valve to facilitate the removal of water from gas wells having two or more gas productive zones disposed vertically along their bore. The valve is adapted to form a connection between a segregation packer and a well tubing string. In use, the valve and the segregation packer are sunk in the well to a position intermediate an upper gas productive zone and a lower gas productive zone. During normal gas production, the valve is closed and gas is collected from both zones, the gas from the lower zone passing through a vertical passage defined by the valve and continuous with the interior of the well tubing. Incidental water accumulated above the segregation packer can be removed by opening the valve and using the gas pressure of the lower productive zone to force the accumulated water upwards to the wellhead and out of the well. Once the well bore has been purged of incidental water, the valve is reclosed and normal production resumes.
U.S. Pat. No. 4,593,760 is an additional example of the prior art.